The KDE development team has decided to release another release candidate just before the final release of KDE SC 4.4. This releases does not include any new features from the previous Release Candidate which was released last week. However, it features a lot of bug-fixes from the last Release Candidate.
As the RC has just been released, it has not been built for most linux distros. However, if you are adventurous, you can download it from download.kde.org and compile it yourself. You can find more information about KDE SC 4.4 RC 3 here.